Authorities say ventilation is unlikely to be behind mystery infections in hotel quarantine as Victoria plans to review air flow to prevent future virus leaks while introducing some changes already.

Hotel quarantine workers must now wear face shields instead of just N95 masks as the chief health officer admitted the exact cause of transmission in the latest case may never be known.

Other quarantine changes include putting “buffers” between family groups and other guests and staggering food delivery times while CCTV could be installed on all floors of every hotel.

Australia recorded another day of no locally acquired cases as Western Australia’s snap five-day lockdown ended on Saturday and the premier announced WA’s vaccine rollout would begin with priority groups on February 22.

Victoria’s Emergency Services Minister Lisa Neville, appointed to oversee the revamped hotel quarantine program, said the government wasn’t “leaving any stone unturned” in its quest for answers.

“We don’t think this is about ventilation,” she said.

“We rejected a number of hotels … and the ones that we have used throughout this program are hotels that do not share air between rooms and into common areas.

“But we’re looking at (whether) there is anything we can do to strengthen our ventilation systems across the program.”

The moves follow a hotel quarantine worker at Melbourne’s Grand Hyatt hotel testing positive for the highly infectious UK variant of coronavirus and a potential case of guest-to-guest transmission at the Park Royal hotel.

A hotel worker at Melbourne’s grand Hyatt wearing a face mask before shields became compulsory. Photo: AAP

Victoria’s Chief Health Officer Brett Sutton said cause of the 26-year-old man’s infection may remain a mystery.

“I’m not sure we’ll find out exactly what happened,” Professor Sutton said.

“Issues that have been identified in Queensland might be at play here.”

However Professor Sutton said the infection of a woman at the Park Royal, who was staying next door to an infected family of five and tested positive despite having no contact, was an open and shut case.

“It does look like it’s a case of doors being opened at the same time,” he said.

Victoria recorded no new cases on Saturday, as all 17 household and social primary close contacts of the infected hotel quarantine worker returned negative tests. All remain in isolation.

Prof Sutton said it was “early days” and officials wouldn’t feel comfortable the state was in “safe territory” until the end of the 14-day incubation period.

A further 1129 primary workplace and exposure site close contacts have been identified and are being placed in isolation.

Health Minister Martin Foley said 60 per cent of that group have returned negative tests so far.

WA sets date for vaccine rollout

West Australians can expect their most at-risk frontline workers to start getting vaccinated for COVID-10 by February 22.

Premier Mark McGowan and Health Minister Roger Cook on Saturday announced plans for the limited initial rollout, saying the state would get 10,000 doses for key at-risk frontline workers to “tackle the greatest potential threat”.

In step with national plans, WA will prioritise quarantine and international border staff, high risk frontline healthcare workers and aged and disability care staff.

As more vaccine doses become available, six hubs will be set up to administer jabs: Perth Children’s Hospital as well as Albany, Headland, Kalgoorlie, Geraldton and Broome health campuses.

“Our priority is to make sure that any approved vaccine that becomes available can be administered to Western Australians as quickly, safely, and equitably as possible,” Mr McGowan said.

All people over 16 will be recommended to receive the vaccine as soon as it’s available to them. Children under 16 will not receive the vaccine, though this could change in later phases of the rollout, the health minister said.

-with AAP